A milling machine is used to drill holes, cut or plane surfaces, and to otherwise form a rectangular piece of metal stock into some finished shape. In doing this, the head supports a rotating cutter or spindle which is mounted for movement in three dimensions on an orthogonal mechanism. The movement of the orthogonally referenced spindle or cutter must be repetitively duplicated when making more than one unit of the part being machined. When this occurs, the mill is able to form duplicates of the machined part. There are several impediments which interfere with repetitive motion. The primary difficulties arise from tolerance and hysteresis in the mechanisms controlling the table. Ordinarily, the spindle is mounted above or opposite a table which enables movement to form the cuts necessary for machine operation. Tables however are as true as possible but nevertheless they are subject to error in operation. One of the sources of error derives from the lack of parallel alignment between the table and the support under the table. More specifically, the table is constructed on a guide track which is sometimes referred to as a dove tail groove. The dove tail groove is constructed with a lead screw in it which is hand or motor driven to cause the table to travel along the length of the dove tail. When this occurs, the table top traverses as urged by the lead screw but its movement is not necessarily precisely parallel and equidistant as observed at a work piece which is mounted on the table.
As will be understood, the table is able to move in three directions, thus one dove tail and lead screw moves it in the X direction, another moves it in the Y direction and a third moves it in the Z direction. In all regards, it is necessary that the mechanisms provide tracking in this fashion. More importantly, the work piece which is supported on the table is ordinarily held in a vice so that it is not susceptible to movement when contacted by the cutter supported on the spindle. The cutter and spindle might otherwise cause chatter or dancing movement on the table. This is prevented by mounting the work piece in the vice. As will be understood, the work piece in the jaws of the vice is machined by the cutter and the spindle. As the vice is opened and closed to remove the prior work piece and place a new one in it, and the movements of the table are then repeated, the sequence of events characteristically seeking duplication of the work piece runs the risk of movement which is not precisely orthogonally controlled with respect to the cutter in the spindle. Suffice it to say, in this event the tolerance of movement in the table mounting mechanism pose a problem.
The present apparatus provides a mechanism so that the lack of parallelism is finessed and the work piece is then able to travel in a true or parallel fashion with respect to the orthogonal axis defined by the spindle. This is accomplished by mounting blank soft jaws on the vice. The soft jaws are initially machined to form conforming shoulders and faces which have the necessary parallel positions with respect to the orthogonal axis system at the cutter. The axes are then defined with respect to the cutter in the spindle regardless of the lack of parallelism or tolerances that might otherwise occur in the table support mechanism, presumably in all three directions. The soft jaws are thus machined to receive the blank work piece to assure parallelism initially. The soft jaws are then periodically opened and closed as the work pieces are machined. To assure that replication properly occurs as the multiple work pieces are machined and the finished products are then obtained, it is important that the vice mechanism hold the soft jaws in precisely identified locations repetitively. For instance, the soft jaws in the device may be used to machine 100 units of the work piece. Later, the soft jaws may be stored and subsequently restored to the vice and used again to machine another order of 100 work pieces. In this instance, it is necessary to fasten the soft jaws precisely to the vice in precisely repeated and fixed locations whereby soft jaw positioning is assured to thereby enable the second batch of the work pieces to be machined. To assure proper replication from batch to batch, it is necessary to locate the soft jaws at a precise location above the table, and to this end the present disclosure sets forth a vice and jaw mounting mechanism which assures that the soft jaws are placed in exactly the same place time and again. This arises from and relates to the mounting mechanism set forth in this disclosure for mounting the jaws. The jaws are preferably constructed with a pair of spaced circular openings on a mounting bracket. The vice has two registered, fixed mounting surfaces, and in particular utilizes a pair of parallel pins to accomplish registration with clamping so that the soft jaws are restored to precisely the same location with regard to an orthogonal reference in the device.
The present disclosure thus sets forth a bench vice which has a base and left and right fixed jaws. A vice opening mechanism is ordinarily included, and the vice includes a base plate which has a surrounding flange enabling connection to slots on the work table of the milling machine. The fixed or master jaws support registration pins. Conveniently, one of the pins is a simple dowel, and one at the opposite end is accomplished by means of a pointed set screw. The set screw has a tapered point at one end. The set screw point engages a protruding mounting bracket on a soft jaw, and registers in an enlarged conic cavity, and when threaded into the vice, forces the soft jaw with clamping action to thereby register the soft jaw repetitively at the same location with great accuracy. This assists in positioning the soft jaw at a fixed location. Given the fact that the soft jaw is machined with faces and shoulders conforming to the work piece, the machinist is therefore able to set up the equipment for repetitive operation time and again, and thereby remount the soft jaws in precisely the correct location.